The invention relates to a thermogluing composition as well as to its use, in particular for the manufacture of a closing stopper for any opening.
It also concerns a closing stopper for any opening consisting of the thermogluing composition of the invention.
Closing devices have already been proposed to stopper any opening, and, in particular, an opening in a metal part.
For example, closing devices have already been proposed which consist of a plastic material based on polyethylene (PE) and polypropylene (PP), or a mixture of polypropylene and an ethylene-propylene-diene terpolymer (PP/EPDM).
Such a closing device consists of a body made of the desired plastic material having the form of the opening to be closed and it comprises a single or double sealing lip which is usually located in the extension of the body of the closing device.
This closing device was placed in the opening to be closed without any subsequent treatment. However, the seal of this closing device against run off water and dust is weak. In addition, when one applies pressure to this closing device in place, the seal is easily broken.
A closing device was then proposed which consists of a steel body and a bead of hot melt deposited on the peripheral surface of the body. Hooking tabs are arranged at the periphery of the body of the closing device in order to maintain this closing device in place. Once the closing device is positioned on the opening, the assembly is subjected to a passage through an oven, and the glue constituting the bead of hot melt melts and hardens during the cooling of the assembly. Thus, the seal between the closing device and the support of the opening has been achieved. The hot melt used is a glue based on a copolymer of ethylene/vinyl acetate (EVA) and its derivatives.
However, the metal body of such a closing device raises problems during its fitting in the opening to be closed because of its hardness and its lack of flexibility.
To avoid the problem caused by the metal body of the closing device itself, closing devices have also been proposed whose body is made of a plastic material and which comprise a bead of hot melt deposited on the peripheral surface of this body.
The seal of the closing device on the support comprising the opening to be closed is achieved in the same manner as above by passage through an oven.
More specifically, such a closing device generally consists of a body made of polyamide 66 or of an alloy of polyamide and of polypropylene, and the bead of hot melt is a bead of glue based on a copolymer of ethylene-vinyl acetate and its derivatives.
This type of closing device with a bead of glue presents a good seal against run off water, dust, and pressure, but its manufacturing method requires a step for manufacturing the body and a step for manufacturing and positioning the bead of glue. This method is thus long and complicated to use, and it requires, in addition, a specific apparatus.
Thus, it is desirable to simplify the method of manufacturing this type of closing device and to improve its reproducibility.
The invention is intended to overcome the above drawbacks of the closing devices of the prior art by proposing a closing device which consists of one and the same material which, at the time of passage through the oven, allows the closing of the opening, for example, of a metal plate, while at the same time achieving the desired seal against run off water, dust and pressure, and which can be manufactured at low cost, by a simple and reproducible method.
To this effect, the invention proposes a thermogluing composition of the type comprising an adhesive component and a component forming a framework, characterized in that:
a) the adhesive compound is a polymer of ethylene-vinyl acetate (EVA)-maleic anhydride and/or polyethylene (PE) and/or polypropylene or modified to have epoxy functions, and
b) the component which forms the framework is an ester block polyether (COPE) or an amide block polyether (PEBA) optionally mixed with a copolymer of ethylene/propylene, where said copolymer of ethylene-propylene can be replaced entirely or in part by a terpolymer of ethylene-propylene-diene (EPDM).
According to a characteristic of the composition of the invention, said EVA-maleic anhydride contains 0.5-40 wt % of units of vinyl acetate and 0.05-15 wt % of maleic anhydride, the remainder being ethylene.
More preferably, said EVA-maleic anhydride contains 5-25 wt % of units of vinyl acetate and 0.5-10 wt % of maleic anhydride, the remainder being ethylene. It is most preferred for said EVA-maleic anhydride to contain 14 wt % of units of vinyl acetate and 0.5-1 wt % of maleic anhydride.
In a preferred embodiment variant, the polymer of ethylene-vinyl acetate-maleic anhydride is a copolymer of ethylene-vinyl acetate grafted with maleic anhydride.
When the EVA is modified to have epoxy functions, the epoxy functions are preferably contributed by glycidyl methacrylate.
The EVA then preferably contains 1-10 wt % of units of glycidyl methacrylate.
According to an embodiment variant of the composition of the invention, the component forming the framework is an ester block polyether (COPE) whose ester part consists of poly(butylene terephthalate) (PBTP) and whose ether part consists of units of ethylene glycol and/or propylene glycol.
According to another embodiment variant of the composition of the invention, the framework material is PEBA mixed with a copolymer of ethylene-propylene and/or a terpolymer of ethylene-propylene diene, in which the PEBA consists of blocks of polyamide 6 and ether segments based on ethylene glycol and/or propylene glycol, and the diene of the terpolymer of ethylene-propylene-diene, when present, is butadiene.
Preferably, in the compositions of the invention, the ratio by weight between said active component and said framework forming component is between 80:20 and 70:30.
When the framework forming component is an ester block polyether, the preferred ratio by weight between the adhesive component and the ester block polyether is preferably 60:40.
The preferred ratio by weight between the adhesive component and the framework forming component is 75:25, when the framework forming component is a mixture of PEBA and of a copolymer of ethylene propylene and/or EPDM.
The composition of the invention can, in addition, comprise additives such as resins that are sticky to the touch, fire retardant agents, reinforcement agents, antistatic agents, antifungicides [sic; fungicides], anticoagulation agents, stabilizers against decomposition by light or heat, dyes as well as fillers, alone or in mixtures of several of them.
A preferred composition of the invention comprises in addition to the adhesive component and the framework forming component, a resin which imparts stickiness to the touch at cold temperature.
Preferred resins that impart stickiness to the touch at cold temperature are of the glycol ester type, such as diethylene glycol ester and dipropylene glycol ester.
In this case, the composition of the invention preferably contains 0.2-10 wt % of resin which imparts stickiness to the touch, with reference to the total weight of the composition of the invention.
The invention also proposes a closing stopper for any opening made into a metal support, which [stopper] embraces the composition of the invention.
This closing stopper can consist in its entirety of the composition of the invention.
In particular, this closing stopper comprises a surface having dimensions which are larger than those of the opening to be closed as well as a means for hooking into said opening.
This closing stopper can consist in its entirety of the composition of the invention.
According to a preferred embodiment variant of the closing stopper of the invention, the latter consists of a plate which is made of a material having a melting-decomposition temperature which is higher than the maximum temperature reached during the passage through an oven which is used to glue the stopper to its support, and which has dimensions which are larger than the opening to be closed on at least one of its faces, which plate is coated with a film made of a composition of the invention containing a resin which is sticky to the touch at cold temperature.
In this case, the preferred resin which presents stickiness to the touch at cold temperature is a resin of the glycol ester type. In particular, it is preferable to use a diethylene glycol ester or a propylene glycol ester as resin which presents stickiness to the touch at cold temperature.
In this case, the material constituting the plate can always be a composition of the invention without resin which is sticky to the touch, a metal, an elastomer, a honeycombed elastomer, a rigid plastic, polytetrafluoroethylene, a hot melt composition containing an expansion agent which decomposes at a temperature higher than or equal to 140xc2x0 C.
According to a characteristic of the closing stopper according to this embodiment variant, the plate has a thickness of 0.5-5 mm, and the film has a thickness of 0.3-3 mm.
The invention also covers the use of the composition of the invention for the manufacture of a stopper to close any opening of any type of support or any other type of industrial product.